August 1, 2022

Hybrid energy: the best of both worlds

Francesc Filiberto, BNZ, Spain, outlines why solar-wind hybridisation is the next step for  renewable energy in Southern Europe in this article published by Energy Global.

More than 2700 years ago, the great wise man,  Homer, said: “Not vain the weakest, if their force  unite.” Although it is assumed that his phrase  has nothing to do with the world of energy, and  even less with that of renewables, this quote can still be linked  to the sector. So-called ‘green’ energy sources are incredibly  beneficial for the planet, but humans are only at the initial  stage of the development of renewable projects; there are  still many forces that need to be joined in order to achieve  better power with fewer resources. In short, it is a question of  efficiency and, above all, hybridisation. 

This word, which is increasingly used in the world of energy, makes perfect sense when it is explained that its goal is to try  to generate electricity from several renewable energy sources, mainly solar and wind, at a common connection point. This makes it possible, first of all, to optimise the connection points to the grid. Storage systems could even be included that further help to adapt production to demand and take  part in adjustment services. However, this approach raises  hundreds of technical questions about how to achieve perfect  hybridisation. 

Hybrid energy 

The U.S. Department of Energy (DOE) highlights innovative  opportunities to spur joint research on hybrid energy systems  in its last statement ‘Hybrid Energy Systems: Opportunities  for Coordinated Research’. The report, a collaborative  effort among DOE and nine US laboratories, says hybrid  energy systems that integrate multiple generation, storage,  and energy conversion processes can play a major role in  decarbonising the US economy. These systems can produce  high-value commodities such as hydrogen, power industrial  processes, and provide more grid flexibility to increase the  deployment of renewable energy technologies. 

What are the benefits? Is everything as simple as it seems?  It is clear that the biggest advantage is the improvement of  the load factor at the connection points, since the energy  injected through the same node is increased. In addition, from  the point of view of consumption, the quality and stability of  the supply are improved and more stability is provided to the  grid, since solar and wind energy production are relatively  complementary. Observing the production curves of these two  energy sources, it is clear that the peaks of each of the energies  are in different bands, so this complementarity allows the  connection to the grid to be optimised. 

According to the Australian Renewable Energy Agency  (Arena), hybrid technologies have also another benefits, such  as reducing the risk for investors and ensuring immediate  reliability and affordability. They can also support a smoother  transition to more renewable energy generation in the  future. For example, in Australia, the King Island Renewable  Integration project is a world-leading power system that will  supply over 65% of King Island’s energy needs using renewable  energy (wind and solar), reducing the island’s carbon dioxide  emissions by more than 95%. It is necessary to highlight that  King Island is not connected to a mainland electricity supply.  

The main objective of hybridisation has to be to unite  different renewable energies in a single node so that they can  cover a large part of the base load and eventually replace  other technologies, such as nuclear energy, for example.  This could therefore reduce the complexity of the grid and  help make daily energy management simpler. In addition,  hybridisation allows for savings on CAPEX and OPEX of  between 10% and 15% on new renewable projects, according to  the Renewable Energy Sources Producers Association (APPA). 

Impact on the land 

However, on the other hand, it must be taken into account  that renewable energies have an obvious impact on the land  due to the large amount of space required, so a project must  be carefully planned and carried out in order to minimise  its impact on its surroundings. The facilities must be made  as environmentally integrated as possible; they cannot  be designed without taking into account landscape and  environmental criteria just because they produce green energy.  It is a matter of studying the territory well, always considering a  positive impact for all the plants that are designed. 


And herein lies the greatest complexity of hybridisation:  location. Wind farms are located in areas with sufficient wind  resources, sometimes mountainous, while for solar plants a  flatter terrain is preferable. At BNZ, it is studying projects of this  type in the north of Portugal, although there are important  difficulties in developing a solar plant due to the topography of  the territory, which will result in a reduction of the generation  capacity of this kind of energy. In any case, it is clear that both  forms of production can coexist, and it is the designers’ job to  strike a balance between both technologies. 

In some developing countries and regions such as India,  hybridisation has been a major initiative to provide full power  supply to a community without access to electricity. But in  these cases, the landscape and the environment take a back  seat with the aim of prioritising access to electricity in the  community. Also relevant is the Asian Renewable Energy Hub  (AREH) project, which plans to install approximately 7.5 GW of hybrid wind energy with 3.5 GW of photovoltaic energy in  Australia in 2023, with the aim of exporting 40 TWh of clean  energy to Indonesia and Singapore. In Europe, however, the  development of hybridisation lags behind. 

Even so, there are already some pilot projects in the south  of Spain, where, in addition to having a large land area to  develop solar energy, there are also great options to obtain  wind energy. In Cadiz, for example, the southernmost province  of mainland Spain, projects were already initiated in 2018 by  Vestas and EDPR. The latter company also announced the  construction of the first fully commercial hybrid wind and  photovoltaic plants in Spain last year. The idea was to use the  solar capacity that was awarded at the time in the renewable  auction to expand the capacity of four wind farms, taking  advantage of the existing energy evacuation infrastructure  and increasing the production and profitability of the entire  facility. 

Regulation is becoming increasingly favourable to this type  of hybrid projects in Southern Europe. In Spain, Royal Decree  1183/2020 recognises hybrid installations as the combination  of two renewable technology generation modules. In Portugal,  on the other hand, legislation on this aspect will soon be  introduced, and is expected to be even easier to develop.  Meanwhile, in Italy, the geographical conditions of regions  such as Puglia or Sicily, mean that solar and wind energy,  today, already coexist on the same land. 

Hybridisation with storage systems Spanish legislation does not yet regulate hybridisation with  storage systems, although with respect to previous legislation,  it is true that the legal vagueness that existed with regard  to storage in Law 24/2013 on the Electricity Sector has been  eliminated. There are other countries, such as the UK, that  are studying a reduction in the load of the connection to  the transport network for storage, seeking to boost their  integration and favour investment in this essential technology.  Also, the DOE report mentioned above outlines that in  response to recent and dramatic changes to the US electric  grid, the topic of hybridisation is growing in popularity within  discussions related to the evolution of the US energy sector.  Customer-sited systems that combine solar photovoltaics and  battery technologies are being deployed for techno-economic  and resilience benefits. 

So why is it so important to move forward on this point?  Energy hybridisation is interesting because it allows the  connection point to be optimised, while the investment is the  same in each solar and wind plant. But there is a problem,  since with hybridisation it must be assumed that when the  combined production exceeds the maximum capacity of the  connection point, the surplus energy must be discarded. On  the other hand, if when hybridising one or more renewable  technologies, a storage technology was to be available,  its efficiency would also be increased, its generation profile  would be flattened and the use of the natural resource would  be maximised, with it being possible to shift the generation  surpluses from times of maximum resource availability and  low demand to times of peak demand and low resource  availability. 

Some of the currently existing storage technologies are:  hydraulic pumping (PHS), Li-Ion batteries, lead-based batteries,  REDOX flow batteries, sulfur-sulfide batteries, flywheels,  compressed air systems (CAES), zinc-air, supercapacitors  and hydrogen generation, among others. Another emerging  form of storage is the production of green hydrogen, which is  produced by electrolysis from renewable energy. In general,  the hybridisation of renewables and storage translates into a  reduction in installation costs that, in the case of photovoltaics,  is estimated at between 7-8%, according to APPA Renewables. 

But the business model is a bit more complicated because  of the cost of storage systems. There are already some pilot  projects at the international level, but with low profitability. The  reason is the large investment in CAPEX for the storage system,  which means that the cost, also known as levelised cost of  storage (LCOS) of the stored energy exceeds €100/MWh. 

It is therefore necessary to optimise the production costs  of storage systems to reduce their CAPEX. This is perhaps an  achievable goal, shown by the extraordinary cost reduction of  renewable energy production technologies in recent years. 


Given this scenario with the need to lower the cost of storage  systems, one of the tools that can help in this transition  phase is the Next Generation EU Fund. In Spain, for example,  the government proposes allocating part of the fund to the  massive installation of renewable generation parks and the  advancement of new storage technologies such as hydrogen.  As a result, the hope is that this union between these energy  sources with great potential will increasingly become a  reality. 


This article was published in the spring issue of Energy Global magazine.

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